The fact a diesel only injects enough fuel to produce the amount of power needed is where the higher MPG figures come from.

When you are slowing down and the engine RPM is above what RPM the govenor controlled by the throttle is asking for, the IP is injecting almost no fuel into the cylinders.

When the RPM is lower than the govenor is asking for at say wide open throttle, you start to see black smoke. The Ip is increasing the amount of fuel injected into the cylinder. You are approaching the point of overfueling the amount of air in the cylinder.

So in that respect, lean and rich are normal diesel operation.
Lean slows you down, rich makes you try to go faster.

 

archangel, about biofuel as a cleaner. Its probably one of the most effective fuel system cleaners you can use.

Its actually so effective that it can tear off deposites that can build up over decades of normal use.

I read a report of a pilot project to run B20 in Victoria BC a little while ago (commercial fleets), they observed a purge period of about two weeks after initially runing biodiesel, the fuel filter should be changed.

The only guys that didn't change the filter as recomended were the mail service, and they noticed some moderate drivability proplems as result (duh).

It also has the ability to accellerate the decomposition of dinodiesel, so my guess is that it can clean it up as well.



As for the difference between diesel and gas...

Diesel is also injected at TDC as opposed to a gasser which has to take precise amounts of fuel and air and then set it on fire.

With diesel, the fuel is injected into a oxygen rich enviorment thats also at high pressure and heat, so it burns as its injected, and there is a reduced chance of incomplete burn as the byproducts spread out of the prechamber.

Ofcourse, once you use up the amount of air thats in the combustion chamber, overfueling starts, and we start to see the trademark black smoke. Unlike gassers, diesels will continue to make more power even in the early stages of overfueling.